The accumulation of bacterial biofilms on tooth surfaces (dental plaque) is responsible for some of the most widespread bacterially induced diseases of man. These diseases include both caries and periodontal disease. Current treatment regimes for most plaque related diseases requires the mechanical removal of plaque/causative microorganisms, by drilling away of infected enamel and dentine for caries lesions, or by root surface debridement in chronic periodontitis, a labor intensive and unpleasant procedure which scrapes the plaque away from inside the periodontal pocket. Because these diseases are associated with specific microorganisms, or groups of microorganisms, there is an increasing interest in the use of antimicrobials to supplement these mechanical procedures. This proposal concerns the development of a new antimicrobial photosensitizing agent for use in the dental industry for the treatment of various oral diseases, including caries lesions and periodontitis. Antimicrobial photodynamic therapy (PDT) offers an attractive alternative to other topical antimicrobial agents. A photosensitizer can be applied directly to the infection site, and in the presence of light, microorganisms can be eradicated in seconds or minutes. Bacteria are unlikely to develop a resistance to this type of agent, and the disturbance of the normal microflora in the mouth can be avoided since the agent is applied at the site of the plaque/infection. During the Phase I project, Lynntech will provide a sound technical basis for a new antimicrobial photosensitizer for therapeutic use in the dental industry for dental plaque related diseases. Relevance to Public Health: A way to effectively kill bacteria within dental plaque could have an enormous impact on the field of dentistry, allowing dentists the means to avoid drilling of infected dentine in a cavity before restoring a lesion, making the procedure less traumatic for the patient and quicker for the dentist. The new photosensitizer also has the capability of treating periodontitis avoiding the drawbacks associated with antibiotic therapy, providing faster killing times and no bacterial resistance. [unreadable] [unreadable] [unreadable]